By Dr Nicola Gan, Consultant, Vitreo-retinal Service, National Healthcare Group Eye Institute,
Tan Tock Seng Hospital
The NHG Eye Institute at TTSH
continues to address the
increasing demand for eye care
services, with active participation in
ophthalmic research and training.
The Institute provides services in the
entire spectrum of ophthalmic
sub-specialities and delivers quality
primary and tertiary eye care to
patients in Singapore and the
region. In part four of the ‘Eye
Discoveries’ series by the NHG Eye
Institute, we take a look at recent
global trends in the treatment of
Diabetes related eye disease.
Diabetes mellitus is a growing health
problem. Recent global estimates
show that 415 million people have
been diagnosed with the disease1. In
2010, 2.5% of the 32.4 million
people who were certified blind and
1.9% of the 191 million people with
visual impairment worldwide were
attributed to diabetic retinopathy,
with an increase in numbers since
19902. The main causes of loss of
vision in diabetic eye disease
Figure 1 – (a) Optos® wide-field fundus photo
of right eye with tractional retinal detachment
involving the disc and nasal retina and vitreous
haemorrhage obscuring details of the rest of
the fundus (b) Left eye with high risk PDR
– neovascularisation of the disc and retina
with pre-retinal and vitreous haemorrhage
(c) Optos® wide-field intravenous fluorescein
angiography of the right eye showing leakage
from retinal neovascular fronds in detached
retina (yellow arrows) (d) Left eye with diffuse
capillary dropout (blue arrows) and leaking
retinal neovascular fronds around the disc
(yellow arrows).
include high-risk proliferative
diabetic retinopathy (PDR) with
tractional retinal detachment,
vitreous haemorrhage, diabetic
macular edema (DME) and macular
ischaemia.
Diabetic Retinopathy (DR)
DR is an end-organ microangiopathy
and a marker that other end-organ
complications such as diabetic
nephropathy or peripheral
neuropathy may also be present.
The severity of DR varies, ranging
from non-proliferative (mild,
moderate, severe) to proliferative
(low-risk, high-risk) disease.
In non-proliferative DR, patients
are mostly asymptomatic and fundus
features include retinal
microaneurysms, intraretinal
haemorrhages and hard exudates.
By the time patients are
symptomatic, DR is usually in the
proliferative stage with optic disc
and retinal neovascularisation and
complications including vitreous
haemorrhage and tractional retinal
detachment. In these cases, patients
may complain of a sudden onset of floaters from vitreous haemorrhage,
or progressive blurring of vision as
the macula becomes involved. The
gold standard of treatment for PDR
is pan retinal laser photocoagulation
to reduce the risk of severe vision
loss3. In patients with high-risk PDR
with tractional retinal detachment
involving the macula or non-clearing
vitreous haemorrhage, vitrectomy
surgery is indicated.
_200117.jpg)
Paradigm shift in the treatment
of Diabetic Macular Edema
(DME)
Five years ago, clinically significant
diabetic macular edema was mainly
treated by macular focal or grid
laser photocoagulation, which was
the gold standard of treatment for
two decades4. However, laser
photocoagulation cannot be used to
treat DME involving the foveal
centre, as laser scars close to the
foveal centre permanently impair
central vision. With the advent of
multiple international large
randomized controlled trials,
intravitreal injections of antivascular
endothelial growth factor
(anti-VEGF) has become an
important advance in the treatment
of centre-involved DME5. FDA approved
drugs include Lucentis®
(ranibizumab) and Eylea®
(aflibercept). A cheaper option is
Avastin® (bevacizumab) which has
been used off-label to treat DME
worldwide. In certain patients,
intravitreal steroid injections are
also a suitable option but with
increased risks of intraocular
pressure rise and cataract
formation. Different treatment
protocols have been adopted by
retina specialists including monthly
injections, monthly monitoring visits
with pro-re-nata injections or a
treat-and-extend regimen.
_200117b.jpg)
The severity of DME and treatment
response can be closely monitored
with clinical examination and OCT
(optical coherence tomography)
scans at each visit. These highresolution
laser interferometry scans
show a cross-section of the macula
and any intra-retinal fluid present.
Personalising treatment
by tailoring treatment intervals to
the individual’s response is the key
to successfully treating DME. Recent
studies on anti-VEGF injections for
centre-involved DME have shown
that the first 3 years are the most
important, with a decline in the
frequency of treatment needed
thereafter6.
Currently, the role of macular focal
or grid laser photocoagulation still
exists for patients with clinically
significant macular edema which
does not involve the fovea7. New
lasers on the market include subthreshold
micropulse diode lasers
that can treat even foveal-involving
DME due to the enhanced duty cycle
technology that minimises macular
damage8. However, this has not been
adopted in many centres worldwide,
as larger randomised controlled
trials are still lacking.
Systemic control - Optimising
care of patients with diabetic
eye disease
Eye screening should be performed
upon diagnosis of diabetes mellitus,
and at least annually thereafter if
no diabetic eye disease is found, or
more frequently if DR or DME is
present. In patients with diabetic
eye disease, intensive control of all
vascular risk factors including
glycaemic control9, cholesterol
levels10 and blood pressure11 are
essential to reduce the progression
of DR. Education on the importance
of regular exercise, a healthy
balanced diet and compliance with
family physician and ophthalmology
check-ups is critical in empowering
patients to take control of their own
well-being. Teaching patients to
keep track of their HbA1c levels as a
gauge of diabetes control is helpful
in involving patients in their own
health care.
Communication between the family
physician and ophthalmologist is
important to ensure holistic care.
Patients must be advised that an
annual eye screen is essential even
if glycaemic control is excellent. DR
screening may be in the form of
diabetic retinal photography (DRP)
screening or a visit to the
ophthalmologist. Currently, family
doctors may refer patients to
polyclinics or Community Health
Centres for DRP screening. A fundus
photo is taken and the photo is
assessed by family doctors or sent
to ophthalmologists in the public
hospitals for grading through the
national SiDRP (Singapore
Integrated Diabetic Retinopathy
Programme) system. The NHG Eye
Institute at TTSH actively
participates in this programme.
Patients who are found to have features suggestive of DR, DME or other retinal problems will
be referred to an ophthalmologist for further evaluation.
Learning points
Blindness from diabetic eye disease is preventable. A recent
epidemiological review found a decline in the incidence of
blindness due to DR in developed countries, with DME overtaking
PDR as the increasingly common cause of visual impairment2.
Annual eye screenings are essential for all diabetics, and early
referrals to an ophthalmologist for assessment and treatment
before the onset of irreversible visual impairment is crucial for all
patients with suspected diabetic eye disease. Optimisation of
vascular risk factors and patient education are important areas in
which the family physician can work on, in a collaborative effort
to reduce the growing burden from diabetic eye disease.
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References
- Ten emerging trends in the epidemiology of diabetic retinopathy. Ophthalmic Epidemiol 2016; Aug
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- Global estimates on the number of people blind or visually impaired by diabetic retinopathy: a metaanalysis
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- Ten emerging trends in the epidemiology of diabetic retinopathy. Ophthalmic Epidemiol 2016; Aug
23(4):209-22.
- Global estimates on the number of people blind or visually impaired by diabetic retinopathy: a metaanalysis
from 1990 to 2010. Diabetes Care 2016; Sep 39(9): 1643-9.
- Photocoagulation treatment of proliferative diabetic retinopathy. Clinical application of Diabetic
Retinopathy Study (DRS) findings, DRS report number 8. The Diabetic retinopathy study research group.
Ophthalmol 1981 Jul;88(7):583-600.
- Early Treatment Diabetic Retinopathy Study Research Group. Photocoagulation for diabetic macular
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- Randomized trial evaluating ranibizumab plus prompt or deferred laser or triamcinolone plus prompt
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- Intravitreal ranibizumab for diabetic macular edema with prompt versus deferred laser treatment:
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- Effect of focal/grid photocoagulation on visual acuity and retinal thickening in eyes with non-centerinvolved
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- Sub-threshold micro-pulse diode laser treatment in diabetic macular edema: a meta-analysis of
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- The effect of intensive therapy of diabetes on the development and progression of long-term
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- Effect of medical therapies on retinopathy progression in type 2 diabetes. The Accord Study Group and
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